Sports is one of most important activities of adolescents, garnering them respect and admiration from peers and elders alike. Yet, prior research on the effects of sport participation on youths' health and development have produced conflicting findings, some finding a deterrent effect and others finding that sports fosters youths deviance. A review of this literature, however, reveals pervasive methodological flaws in assessing the youth sport-development association. That is, prior research tends to: 1) rely on cross-sectional samples that fail to account for potential selection processes; 2) fail to control or important confounding influences on the association; 3) treat all sport participation experiences and all deviance as the same; and, 4) generally fails to theorize and test the gendered effects of sport participation on youth health and development. This study uses de-identified secondary data from the NICHD's Study of Early Child Care and Youth Development to address these limitations in prior research by examining the effects of types and intensity of sport participatio on deviance, aggression, substance use, and sexual behavior as youths age from the sixth grade to age 15. This project has two specific aims: 1) estimate multivariate models that assess the predictive power of the intensity and types (individual versus non-contact team versus violent team) of sport participation on youths' health and delinquency; and 2) examine gender differences in effects of sport participation on delinquency. Results from this project will inform research on the causes of youth delinquency and place sport in its proper context in youth's lives, particularly in regards to how sports affects boys and girls differently as a determinant of health and development.